The potential non-equivalent defects in both 3C- and 4H-SiC were classified by a new method that was based upon symmetry considerations. In the case of 4H-SiC, their number was considerably higher than in 3C-SiC, since the hexagonal symmetry led to diversification. The different theoretical methods hitherto used to investigate defects in 3C-SiC were critically reviewed. Classical MD simulations with a recently developed interatomic potential were employed to investigate the stability, structure and energetics of the large number of non-equivalent defects that may exist in 4H-SiC. Most of the potential defect configurations in 4H-SiC were found to be stable. The interstitials between hexagonal and trigonal rings, which did not exist in 3C-SiC, were characteristic for 4H-SiC and other hexagonal polytypes. The structure and energetics of some complex and anisotropic dumb-bells depend strongly on the polytype. On the other hand, polytypism did not have a significant influence on the properties of the more compact and isotropic defects, such as vacancies, antisites, hexagonal interstitials, and many dumb-bells. The results allow conclusions to be drawn about the energy hierarchy of the defects.

A Comparative Study of the Structure and Energetics of Elementary Defects in 3C- and 4H-SiC. M.Posselt, F.Gao, W.J.Weber, V.Belko: Journal of Physics - Condensed Matter, 2004, 16[8], 1307-23